The present invention relates to the field of double overhead cam shaft type V type internal combustion engines, and more specifically relates to a novel configuration for such an engine which has an odd number of cylinders in each of its two cylinder banks, which provides good manufacturability and operational characteristics for the engine.
A V type internal combustion engine of a so called double overhead cam shaft configuration is per se known. Each cylinder bank of such an engine has, provided along its cylinder head, an intake cam shaft and an exhaust cam shaft, each of which is provided with cams which typically press directly on the ends of valve stems of intake and exhaust poppet valves for the cylinders of that cylinder bank. This construction is inevitably complicated and has a large number of components, and accordingly it is desired to simplify it by reducing diversity of parts to as great a degree as possible, from the point of view of manufacturing convenience and reduction of cost, as well as from the point of view of minimizing the problems of parts stocking and inventory. Yet, in the prior art, because all the parts for the left and right cylinder heads and their associated valve gear such as the intake and exhaust cam shafts have been different, a great diversity of components has persisted. In this connection, reference should be made to copending patent application Ser. No. 780,609, assigned now U.S. Pat. No. 4,610,224 or under an obligation of assignment to the same assignee as the present patent application, which suggests a new configuration for such cylinder heads and their associated valve gear which allows the cylinder heads and the cam shafts of the left and right cylinder banks to be identical but reversed in orientation; however, it is not intended hereby to admit said copending patent application as prior art to the present application except to the extent otherwise required by law.
Further, all these four cam shafts are required to be driven from the crank shaft of the engine in a determinate phase relationship therewith. Accordingly, drive means must be provided for driving each of them. If all these four cam shafts are individually driven directly from the engine crank shaft, as has heretofore been practiced as for example via a timing chain or drive belt, then the problem arises that it is hard to make the engine compact.